How Spring MVC Simplifies Server‑Side Development: From Servlets to DispatcherServlet

1. The Former King – Servlet

Early Java web development relied heavily on Servlets, which handled request reception, processing, and response generation by wrapping raw HTTP data into HttpServletRequest and HttpServletResponse objects, allowing developers to focus on business logic.

2. Wanting to Go Further

Using plain Servlets becomes cumbersome as applications grow: each Servlet handles a single request, manual parameter extraction and validation are required, URLs are hard‑coded in web.xml, and Servlets are tightly coupled with view technologies.

3. Spring MVC – Two‑Level Controllers

Spring MVC introduces a front‑controller called DispatcherServlet , which acts as a “super Servlet”. Business‑logic classes are no longer Servlets but ordinary POJOs called Handlers (often implemented as Controllers ).

4. DispatcherServlet – Front‑Controller

The DispatcherServlet is the core of Spring MVC. It centralises request handling, performs automatic parameter binding, validation, URL matching, view resolution, and data rendering, effectively orchestrating the entire request‑processing flow.

5. HandlerMapper – Request Mapping Expert

Spring MVC replaces the static web.xml mapping with HandlerMapping implementations that associate request URLs with specific Handlers. Common strategies include SimpleUrlHandlerMapping, ControllerClassNameHandlerMapping, BeanNameUrlHandlerMapping, and the annotation‑driven @RequestMapping via DefaultAnnotationHandlerMapping.

6. HandlerInterceptor – Intercepting Requests

Before a request reaches a Handler, HandlerInterceptor s can pre‑process it (e.g., authentication, logging). Unlike Servlet Filter, an interceptor works at the Handler level, offering finer‑grained control.

7. Handler – The Secondary Controller

The Handler (or Controller) contains the actual business logic. Spring MVC isolates this logic from request handling, view rendering, and other cross‑cutting concerns.

8. HandlerExecutionChain – Bridging Handler and Interceptor

HandlerExecutionChain combines a Handler with its associated HandlerInterceptors, forming a chain of responsibility. The request passes through each interceptor; if all return true, the Handler is finally invoked.

9. ModelAndView – Decoupling Data and View

After processing, a Handler returns a ModelAndView object that holds the data model and the logical view name, separating business results from navigation concerns.

10. ViewResolver – Finding the View

The ViewResolver translates the logical view name into a concrete View implementation (e.g., JSP, FreeMarker, Velocity, XSLT, JasperReports). Various resolvers include BeanNameViewResolver, InternalResourceViewResolver, FreeMarkerViewResolver, etc.

11. View – Rendering the Data

The selected View renders the model data into the final response (HTML, JSON, PDF, etc.) and returns it to the DispatcherServlet, which writes it back to the client.

In summary, Spring MVC’s architecture—front‑controller, handler mappings, interceptors, execution chain, ModelAndView, view resolution, and rendering—provides a clean, modular approach to server‑side development, vastly simplifying the code compared to raw Servlets.

<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4">
    <servlet>
        <servlet-name>ShoppingServlet</servlet-name>
        <servlet-class>com.myTest.ShoppingServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ShoppingServlet</servlet-name>
        <url-pattern>/shop/ShoppingServlet</url-pattern>
    </servlet-mapping>
</web-app>

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
    <servlet>
        <servlet-name>Spring MVC</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:Spring-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Spring MVC</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
</web-app>